The invention relates protection against damage and malfunctioning caused by exploding power semiconductors. Especially, the invention relates to installations for bypassing an exploded power semiconductor, such as an IGBT.
Power semiconductors, such as IGBTs (Insulated Gate Bipolar Transistor) or GTOs (Gate Turnoff Thyristor), are used in the field of power transmission systems for converting electrical current. In such systems, a series of modules comprising a semiconductor may be arranged in branch, one for each phase, of a converter. Such converters are used for conversion between AC and DC. In the event of a malfunctioning semiconductor, such systems have been adapted to bridge or bypass this faulty semiconductor or the installation module of the semiconductor.
US 2009/0141416 (D1, see abstract of D1) shows a device for short-circuiting power semiconductor modules. The document describes power semiconductor modules connected to each other in a series circuit. A short-circuiting device is arranged at each power semiconductor module. The short-circuiting device is a pyrotechnical/mechanical element, which has a detonation charge and a tripping device, which can be displaced by the detonation charge.
US 2009/0257165 (D2, see abstract of D2) shows a overcurrent switching apparatus for bypassing an electronic component (9 in figures), such as an IGBT, which includes a carriage (14) for a shortcircuiting contact (19) interconnecting terminals (2, 3), which carriage is driven by a prestressed spring (15).
US 2010/0118453 (D3, see claims of D3) shows an installation of power semiconductors comprising a shortcircuiting device for each semiconductor submodule. The shortcircuiting device includes a vacuum interrupter tube provided with latching and tripping means, which tripping means counteracts the latching means.
U.S. Pat. No. 6,222,284 (D4) also includes a springloaded switch and trip release device (see FIG. 1d (ii) of D4).
A problem with such bypassing devices, which includes bypassing means that are released during a failure, is that they may also be released accidentily without any failure and cause unnecessary disruption of, for example, power transmission.
US 2010/0314775 (D6) describes an explosion-resistent module structure for power semiconductor components (such as IGBTs). It includes a hollow space filled with particles (5 in FIG. 1 of D&) arranged on top of a power semiconductor (1). The particles are electrically conducting spherical particles that during a short circuit conducts the current. The construction reduces the explosion pressure by providing channels for escape of explosion gas. Thus, D6 provides a protection that cannot be released accidentally.
However, the module of D6 cannot provide a reliable permanent current conducting upon a shortcircuiting failure (see §0007 of D6).
Moreover, in the field of explosion resistant installations of power semiconductors, document U.S. Pat. No. 6,295,205 (D7) describes a protective casing for a power semiconductor (such as an IGBT), which includes an expandable protective sheath for catching fragments from an exploding power semiconductor. One protective sheath is installed enclosing each power semiconductor module. The protective sheats can be made of a fabric that includes Kevlar (aramid fibers made of para-phenyien-terephthaiamide (PPTA). D7 provides a protection from high velocity fragments from an explosion, but does not describe disconnection of a faulty power semiconductor.